(a) Field of the Invention
The present invention relates to a machine-tool of the type provided with a horizontal rotative spindle, the frame of which is a closed porch-shaped frame.
(b) Description of the Prior Art
Machine-tools of the foregoing type, most generally boring or reaming machines, generally have a spindle support which is situated between the vertical pillars of the porch-shaped frame between which it moves vertically. So far as the workpiece-carrying table is concerned, it is mounted in front of said porch so as to be able to move in two mutually perpendicular directions, one of which is transverse, that is to say perpendicular to the axis of the spindle, and the other one of which is longitudinal, that is to say parallel to this axis.
The drawback of this arrangement lies in the fact that, when the table is largely out of the center of the frame, in the neighbourhood of one or the other of its extreme lateral positions, the frame of the machine receives a deformation such that the accuracy of machining is jeopardized. The effect of this deformation is more serious as the point at which machining is effected is spaced from the surface of the table, in other words the bad effect of the deformation of the frame becomes more important when the spindle is situated at a high level. The reason is that the rocking movement impelled to the workpiece due to the deformation of the frame can be considered as having its center in the vicinity of the surface of the table and, consequently, is amplified by the distance between this table and the machining point.
Another drawback due to the conventional construction of such machines lies in the fact that, the space within the porch being occupied by the spindle support which must be able to move therein entirely, it is not possible to employ measures to control the deformation of the frame, for instance by using laser rays, since the latter would be intercepted by the spindle support.
These machines moreover have the drawback that they occupy, in front of the porch, a large space in the widthwise sense, due to the fact that the table must be able to move transversely. This is not convenient for the distribution of the accessories of the machine and, especially, prevents a tool changer being placed in front of the porch.